For instance, two types of driving support control are known. One is driving support control (hereinafter also referred to as lane maintaining control) to maintain an own-vehicle in a traffic lane along a lane mark, and is also called lane keeping control. The other is driving support control (hereinafter also referred to as path following control) to cause an own-vehicle to follow the path of a preceding vehicle.
For instance, Japanese Unexamined Patent Application Publication No. 2005-332192 (paragraphs [0043] to [0046]) discloses that lane maintaining control and path following control are performed. Specifically, it is disclosed that when a preceding vehicle is running away from the own-vehicle, a target running path of the own-vehicle is set based on a lane mark, and when a preceding vehicle is running close to the own-vehicle, a target running path of the own-vehicle is set based on the position of the preceding vehicle.
In the lane maintaining control, it is necessary to capture and recognize a lane mark presented ahead by an in-vehicle camera or the like. However, there are many locations (for instance, intersections) on general roads where a lane mark is discontinued, and cases frequently occur where there is no lane mark to be captured by a camera. Also, when the own-vehicle is running at a low speed due to traffic congestion or the like, the own-vehicle may approach a preceding vehicle and the lane mark ahead may be blocked by the preceding vehicle. Then, cases occur where a lane mark may not be captured by a camera or the like. For this reason, when the own-vehicle is running on a general road or running at a low speed, the lane maintaining control may not be performed in some cases. For instance, Japanese Unexamined Patent Application Publication No. 2000-168395 (paragraph [0038]) discloses that while the lane maintaining control is performed, when the vehicle speed of the own-vehicle becomes less than or equal to a predetermined vehicle speed, driving support control performed up to now is cancelled.
When a vehicle capable of performing lane maintaining control and path following control performs the path following control on a highway, a preceding vehicle may move to a branch traffic lane and disappears from the area ahead of the own-vehicle. According to Japanese Unexamined Patent Application Publication No. 2000-168395, in this situation, when the own-vehicle is running at a low speed due to traffic congestion or the like, the driving support control is automatically canceled. Then, a driver is unable to receive the driving support, and the operational burden of the driver increases.